Are there any links to research which would suggest an optimum or maximum number of times for ablation on the same heart? Do chances of stopping AF symptoms change with each surgery?
This is a subject I'm very well versed in since I've had paroxysmal atrial fibrillation (PAF) and atrial flutter (AFL) for a number of years and I've undergone no fewer than five ablation procedures. However, I really can't improve on M. Arrowsmith's answer. It's pretty much spot on. However, I will add some thoughts you won't easily find in published research.
The optimal number of ablations is, of course, one. And for the majority of patients that's how many they'll undergo. Success rates for PAF are very high these days. However, a significant number of patients will require two, with the second one often being described as a "touch up" procedure. There are two major reasons why a second ablation is often required:
First, it is very easy for the electrophysiologist (EP) to accidentally create what's known as a flutter circuit during the procedure. This usually takes the form of a tiny gap in the line of burns that are created to contain the afib. That tiny gap allows an errant signal to begin a self-perpetuating circle in the heart that causes the heart to beat very rapidly, often at about 150 beats per minute. This is atrial flutter (AFL). It's similar to AF, but unlike AF it's a very regular rhythm, and it's usually faster. Rates of 150 beats per minute are common. A second ablation to fix AFL is typically much faster and simpler than the original AF ablation.
Second, the standard ablation for AF is what's known as pulmonary vein isolation (PVI). A PVI ablation procedure creates a circle of burns around the point in the left atrium where the pulmonary veins enter. Pulmonary veins are the number 1 source of errant AF signals, so burning a circle around them basically creates a "fence" that contains the errant signals and doesn't let them spread to the rest of the atria. However, there can also be isolated spots elsewhere in the atria that generate errant AF signals and those are very difficult to find. Since they're difficult to find, they can be missed during the first procedure and require a second procedure to go in and find and ablate them individually.
After a second ablation, additional ablations are going to be because:
The EP's skills or experience are lacking. Ablations require a great deal of experience, practice and a precise touch. Operator experience counts for a lot. You should seek the EP who does a LOT of ablations.
The patient is a difficult case with unusual sources of afib that are difficult to find or are in difficult locations. Sometimes those locations can be places that are simply too dangerous to ablate. (This is my situation.)
Sometimes, after a period of time, connections can reestablish themselves. Natural healing around the ablation lesions creates a new pathway that allows afib to escape "the fence" and thus AF reappears.
Do chances of stopping AF symptoms change with each surgery?
Yes, they improve. With PAF the first procedure will completely stop AF symptoms for about 70-75% of all patients. A second procedure raises that number into the 90-95% range. So the chances of an ablation stopping your AF for years or even permanently are very good, but as I have learned, a small percentage of patients will not be so lucky.
On the other hand, if you have longstanding, persistent AF, the success rates are not as good. With persistent AF you're looking at about a 50-60% success rate overall.
In 2013, a systematic review and meta-analysis (see ref in source) examined the long term outcome of catheter ablation in patient with atrial fibrillation.
They first looked at single procedure success rates (=percentage of patients free of atrial arrhythmia or not requiring a second procedure at 12 months) and reported that the pooled overall success rate was 64.2% (95% CI 57.5% to 70.3%).
If paroxysmal atrial fibrillation (PAF) and non paroxysmal atrial fibrillation (PAF) were considered separately:
The pooled 12-month success rate for the 11 studies reporting outcomes for PAF patients was 66.6% (95% CI 58.2% to 74.2%), and for the 6 studies reporting outcomes for NPAF patients, it was 51.9% (95% CI 33.8% to 69.5%).
They then looked at multiple procedure success rates and showed that the overall multiple-procedure long-term success rate was 79.8% (95% CI 75.0% to 83.8%) in 13 studies (Figure 3).
The multiple-procedure long-term success in PAF was 79.0% in 8 studies (95% CI 67.6% to 87.1%), and that in NPAF was 77.8% in 4 studies (95% CI 68.7% to 84.9%, P=0.9 versus PAF).
Here a graph representing the different in success rates between single procedures and multiples procedures:
All these results have to be taken with caution as the heterogeneity associated with these results exceeded 50% but it provides a general overview.
Several studies have suggested some variables associated with AF recurrence such as NPAF, left ventricular systolic dysfunction or heart failure, structural or valvular heart disease, and duration of AF.
Finally, I don’t think it is possible to define an optimum number of ablation. Ideally, the aim is to success after the first ablation. I haven’t heard of a maximum. From my experience, if AF can’t be effectively ablated, the aim is to achieve frequency/rhythm control through optimal drug therapy until the patient in asymptomatic.
Sources (for text and figure): Ganesan et al. Long-term Outcomes of Catheter Ablation of Atrial Fibrillation: A Systematic Review and Meta-analysis. J Am Heart Assoc. 2013; 2: e004549 originally published March 18, 2013 doi: 10.1161/JAHA.112.004549